JPH01201320A - Acrylic composition for forming porous product, pressure-sensitive adhesive tape produced by using same and its production - Google Patents

Abstract

PURPOSE:To form a composition which is excellent in applicability such as an ability to coat and can give a sheetlike porous cured product excellent in buffering property to shocks, noises, heat, etc., flexibility, heat resistance, durability, etc., by mixing an isocyanate-reactive acrylic low-MW copolymer with a polyisocyanate and a pore-forming agent. CONSTITUTION:This acrylic composition for forming a porous product comprises an acrylic low-MW copolymer having 1.6-3.5 functional groups reactive with an isocyanate group, a polyisocyanate and a pore-forming agent and is produced so as to give a flexible sheetlike cured product having many pores. By applying an acrylic adhesive layer to a flexible sheetlike cured product comprising said composition and having many pores, a pressure-sensitive tape excellent in flexibility, resistant to delamination and excellent in creep resistance can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a method for obtaining a porous cured material in the form of a sheet having excellent cushioning properties against impact, sound, heat, etc., flexibility, heat resistance, and durability. The present invention relates to an acrylic composition for forming porous objects, a pressure-sensitive adhesive tape that allows the porous cured product thereof to be easily attached to an adherend, and a method for producing the same.

Conventional technologies and issues Previously, urethane foam sheets for the purpose of shock mitigation, soundproofing, heat insulation, etc., and pressure-sensitive adhesive tapes with an acrylic adhesive layer added to them to allow easy attachment to adherends have been proposed. (Japanese Unexamined Patent Publication No. 52-89140).

However, urethane foam sheets have a problem in that they are inferior in durability such as weather resistance and heat resistance.

In addition, when using a urethane foam sheet as a pressure-sensitive adhesive tape, adhesion of an acrylic adhesive layer directly to the urethane foam sheet results in poor adhesion, so it is necessary to treat the surface of the foam sheet with good adhesion in advance. There was a problem. Furthermore, depending on the application, waterproof properties may be required, but in that case it is necessary to surface-treat the foam sheet with a water-repellent agent in advance, which poses a problem in that it is difficult to achieve both the above-mentioned good adhesion treatment.

Means for Solving the Problems In order to overcome the above-mentioned problems, the present inventors have conducted extensive research, and as a result, have made it possible to harden an acrylic low molecular weight copolymer with a polyfunctional isocyanate. It was discovered that the object could be achieved by a composition containing a pore-forming agent, and the present invention was completed.

That is, the present invention comprises an acrylic low molecular weight copolymer having 1.6 to 3.5 functional groups capable of reacting with isocyanate, a polyfunctional isocyanate, and a pore-forming agent, and has a large number of pores. An object of the present invention is to provide an acrylic composition for forming a porous material, which has the following properties and is capable of producing a flexible sheet-like cured product.

The present invention also provides a pressure-sensitive adhesive tape in which an acrylic adhesive layer is adhered to a flexible sheet-like cured product having a large number of pores and made of the above-mentioned acrylic composition for forming porous objects. This is what we provide.

Furthermore, the present invention applies the above-mentioned acrylic composition for forming a porous material on the acrylic adhesive layer of the adhesive sheet, and if necessary, further applies an acrylic adhesive layer on the coated layer. The present invention provides a method for manufacturing a pressure-sensitive adhesive tape by stacking sheets and heat-treating the sheets.

By curing an acrylic low molecular weight copolymer having 1.6 to 3.5 functional groups that can react with isocyanates with a polyfunctional isocyanate, it has excellent flexibility, cushioning properties, and weather resistance. It becomes possible to form a sheet-like porous cured body having excellent durability and heat resistance. In addition, the type and composition of the component monomers of the acrylic low molecular weight copolymer,
By changing the type of polyfunctional isocyanate used as a crosslinking agent, the proportion of pores, etc., the physical properties of the resulting cured product can be easily adjusted.

On the other hand, by using an acrylic pressure-sensitive adhesive, it is possible to obtain a pressure-sensitive adhesive tape that has excellent adhesive strength with such a porous cured body. In particular, by applying a porous material-forming acrylic composition to the adhesive layer and heat-treating it to form a pressure-sensitive adhesive tape, strong adhesive strength is developed and delamination is prevented. It can be used as a wake-up.

Examples of Constituent Elements of the Invention The acrylic composition for forming porous materials of the present invention contains a low molecular weight acrylic copolymer, a polyfunctional isocyanate, and a pore forming agent.

As the low molecular weight acrylic copolymer, one having a functional group capable of reacting with isocyanate, such as a hydroxyl group or a carboxyl group, is used. The preparation of such acrylic low molecular weight copolymers includes, for example, acrylic acid,
Monomers having a functional group that can react with isocyanates such as methacrylic acid, hydroxyethyl acrylate, arsenic methacrylate, and droxyethyl acrylate, and monomers having a carbon number of 12 or less such as ethyl acrylate, methyl methacrylate, butyl acrylate, and ethylhexyl acrylate. An acrylic acid alkyl ester consisting of an ester of acrylic acid or methacrylic acid having an alkyl group, and if necessary, vinyl acetate,
This can be carried out by copolymerization using a modifying monomer such as styrene, vinyl chloride, vinylidene chloride, or acrylonitrile.

The acrylic low molecular weight copolymer used in the present invention includes:
From the viewpoint of workability such as coating work of the resulting composition, or its cushioning properties and flexibility when made into a sheet-like cured product, it is preferable that the average molecular weight is 4,000 to 20,000 and the glass transition point is 250°. The following are preferred. Such a low molecular weight acrylic copolymer can generally be obtained by using 50% by weight or more of the above-mentioned acrylic acid alkyl ester as a main monomer.

Furthermore, the acrylic low molecular weight copolymer used in the present invention is
It has 1.6 to 3.5 functional groups capable of reacting with isocyanate per molecule, preferably 1.9 to 2.8. Such low molecular weight acrylic copolymers generally contain monomers having functional groups capable of reacting with isocyanates in a proportion of 0.2 to 0.2% of the total amount of monomers.
It can be obtained by using 20 mol%. If the number of functional groups is less than 1.6, the formed cured product will have poor strength, and if it is made into a sheet-like cured product with more than 3.5 functional groups, the cured product will have poor cushioning properties and flexibility. . From the viewpoint of strength and flexibility, those having a functional group capable of reacting with isocyanate in the molecular chain or at the end of the molecular chain are preferably used. Such low molecular weight acrylic copolymers may be prepared by using a polymerization initiator having a functional group capable of reacting with isocyanates such as azobisisocyanovaleric acid or azobiscyanopentanol, or by using a polymerization initiator having a functional group capable of reacting with isocyanates such as azobisisocyanovaleric acid or azobiscyanopentanol, or by using a polymerization initiator having a functional group capable of reacting with isocyanates such as mercaptoethanol, dioglycolic acid, It can be obtained by polymerization using a chain transfer agent having a functional group capable of reacting with isocyanate such as aminoethyl mercaptan, or by using both in combination. The amount of polymerization initiator and chain transfer agent used is generally 1
0.1 to 20 parts by weight per 00 parts by weight is suitable.

In the present invention, known polyfunctional isocyanates can be used, and representative examples include polyfunctional isocyanate monomers such as tolylene diisocyanate, diphenylmethane diisocyanate, and isophorone diisocyanate, or those that react with isocyanate. Compounds such as an isocyanate prepolymer made of a reaction product of a low molecular weight acrylic copolymer or a polyoxyalkylene polyol and a polyfunctional isocyanate monomer can be mentioned. The amount of polyfunctional isocyanate used is generally such that the ratio of isocyanate groups is 1 to 3 equivalents to the functional groups that can react with isocyanate in the low molecular weight acrylic copolymer, but is not limited thereto.

Examples of the pore-forming agent used in the present invention include hollow particles and foaming agents.

Hollow particles are used to obtain a cured product having a large number of independent pores. The apparent density is 0. O1~0.5g/
Hollow particles of CD are preferably used. If the apparent density is less than 0.01 g/c-, the strength of the cured product may be poor, and if it exceeds 0.5 g/c-, the flexibility will decrease when made into a sheet-like cured product. It may become scarce. The amount of hollow particles to be used is appropriately determined based on the apparent density, particle size, physical properties of the low molecular weight acrylic copolymer, etc. As the amount used increases, the flexibility of the sheet-like cured product can be increased, but the strength decreases, so it may be determined as appropriate depending on the flexibility and strength of the desired sheet-like cured product based on its properties. . -Generally, 0.1 to 50 parts by weight are used per 100 parts by weight of the acrylic low molecular weight copolymer and polyfunctional isocyanate. Examples of the hollow particles include silica-based hollow particles, aluminosilicate-based hollow particles, shirasu balloons, and organic-based hollow particles, with an average particle size of 1 to 500 μm.
m is generally used.

A cured product having an independent pore structure using hollow particles has the advantage of being particularly excellent in barrier properties such as waterproof and windproof properties.

On the other hand, a foaming agent is mainly used to obtain a cured product with an open cell structure, and a sheet-like cured product with an open cell surface layer is advantageously used to form a pressure-sensitive adhesive tape that has excellent anchoring properties for the acrylic adhesive layer. It will be done.

As the foaming agent, a known foaming agent that generates gas by heating or chemical reaction can be used. Examples include inorganic blowing agents such as ammonium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium nitrite, sodium borohydride, azides, or salts such as water, trichloromonofluoromethane, and dichloromonofluoromethane. Fluorinated alkanes, azo compounds such as azobisisobutyronitrile, azodicarbonamide, barium azodicarboxylate, paratoluenesulfonyl hydrazide, diphenylsulfono, 3.3°-disulfonylhydrazide, 4,4°-oxybis( hydrazine compounds such as benzenesulfonyl hydrazide), allylbis(sulfonylhydrazide), semicarbazide compounds such as ρ-toluylenesulfonyl semicarbazide and 4,4°-oxybis(benzenesulfonyl semicarbazide), 5-morpholyl-1,2,3, Triazole compounds such as 4-thiatriazole, N- such as N,N'-dinitrosopentamethylenetetramine and N,N'-dimethyl-N,N'-dinitrosoterephthalamide;
Examples include organic blowing agents such as nitroso compounds. Note that the foaming agent may be encapsulated in microcapsules.

The appropriate amount of the blowing agent to be used is such that the volume of the coating layer is 1.2 to 100 times larger when foamed, and although it varies depending on the expansion ratio of the blowing agent, it is generally 1 part by weight per 100 parts by weight of the low molecular weight acrylic copolymer. ~300 parts by weight. When using a foaming agent, a foam stabilizer typified by polyoxyalkylene compounds, silicone compounds, etc. is added as necessary.

The acrylic composition for forming porous materials of the present invention is prepared by mixing the above-mentioned necessary components. that time,
A solvent may be used to reduce the viscosity of the mixture if necessary. Furthermore, a curing catalyst made of an organic tin compound or the like may be added to accelerate curing, if necessary. In addition, if necessary, commonly used compounding agents such as foaming aids, fillers, plasticizers, tackifiers, colorants, anti-aging agents, anti-mold agents, ultraviolet absorbers, and antioxidants may be added. good.

By heat-treating the resulting mixture, a cured product having a large number of pores based on hollow particles (or based on foaming of a foaming agent) is formed.The cured product has cushioning properties, rebound resistance, and impact resistance. , has excellent cushioning properties against sound and heat, waterproofness, heat resistance, durability, etc., and is even more flexible when molded into sheets or thin plates.Acrylic systems for forming porous objects using hollow particles. In the case of a cured product made of the composition, an independent pore structure is formed, so it has particularly excellent barrier properties such as waterproof and windproof properties.Therefore, it can be used for various purposes based on these properties. In its application, good workability such as coating properties and good moldability are also advantageous.In addition, when molding, an appropriate method such as a casting method or an extrusion method can be applied.Sheet-like When obtaining a cured product, a method of coating and developing it on a release sheet or the like can also be applied.

The pressure-sensitive adhesive tape of the present invention has a large number of pores and is made of the above-described porous material-forming acrylic composition, and has an acrylic adhesive layer adhered to one or both sides of a flexible sheet-like cured product. That's what happens. Its production is, for example, by spreading an acrylic composition for forming porous objects on a release sheet and heating and curing it to form a sheet-like cured product, and then coating an acrylic adhesive on it. This can be done by a method such as attaching a prepared adhesive sheet through its acrylic adhesive layer. As the above-mentioned pressure-sensitive adhesive sheet, one in which a release sheet is used as a supporting base material so that it can be easily peeled off from the pressure-sensitive adhesive layer after pasting is used. In the case of a sheet-shaped cured product made of an acrylic composition for forming porous objects using hollow particles, the above method also has excellent adhesive strength between the cured product and the adhesive layer, making it difficult to cause delamination, making it suitable for practical use. A pressure-sensitive adhesive tape with sufficient resistance to

To produce a pressure-sensitive adhesive tape with even better adhesive strength between the cured product and the adhesive layer, an acrylic composition for forming a porous material is applied onto the acrylic adhesive layer of the adhesive sheet, and then heat-treated. This can be carried out by a method of curing the applied layer. According to this method, it is possible to obtain a cured product and a pressure-sensitive adhesive layer that are strongly bonded together by crosslinking via a polyfunctional isocyanate, as if they were integrally formed. When applying the above method to obtain a pressure-sensitive adhesive tape having adhesive layers on both sides of a sheet-like cured product, an acrylic composition for forming a porous material is applied on the acrylic adhesive layer of the adhesive sheet. Then, a separate pressure-sensitive adhesive sheet may be superimposed on the coating layer via the pressure-sensitive adhesive layer, and then this may be heat-treated to cure the coating layer.

The adhesive sheet used in the production of pressure sensitive adhesive tape is
Generally, an acrylic pressure-sensitive adhesive layer is provided on a support base material made of a release sheet so that the support base material can be easily peeled off from the pressure-sensitive adhesive layer after pasting.

Acrylic adhesives in pressure-sensitive adhesive tapes are used because of their durability such as weather resistance and heat resistance. There are no particular limitations on the acrylic adhesive used.

The main component is an acrylic acid alkyl ester consisting of an ester of acrylic acid or methacrylic acid having an alkyl group having 12 or less carbon atoms, such as ethyl acrylate, methyl methacrylate, butyl acrylate, and ethylhexyl acrylate, and vinyl acetate and styrene. , vinyl chloride, vinylidene chloride, and functional group-containing monomers to improve adhesion to adherends such as acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, and acrylonitrile. Copolymerized products are generally used, and products in which tackifying resins and the like are blended as necessary are generally used.

Effects of the Invention The acrylic composition for forming porous materials of the present invention has excellent workability such as coating properties. It is possible to obtain a porous hardened material that has excellent cushioning properties such as relaxation, soundproofing, and heat insulation, waterproofness, ITl (durability such as heat resistance and weather resistance, cushioning properties, and rebound resistance), as well as sheets and thin plates with excellent flexibility. Furthermore, when hollow particles are used as a pore-forming agent, a porous cured product that is particularly excellent in barrier properties such as waterproofness and windproofness can be obtained.

The pressure-sensitive adhesive tape of the present invention is based on the porous cured product (
In addition to having particularly excellent flexibility, the material produced by the method of the present invention has excellent adhesive strength between the porous cured material and the adhesive layer, which prevents delamination from occurring, and has excellent creep resistance. . In addition, in the case of a porous cured body made of hollow particles, excellent adhesive strength between the porous cured body and the adhesive layer can also be obtained by directly applying an adhesive layer to the cured body in advance in the form of a sheet. can do.

Examples Reference Example 1 80 parts of 2-ethylhexyl acrylate (parts by weight, the same applies hereinafter), 20 parts of ethyl acrylate, 3 parts of 2-hydroxyethyl acrylate, 2 parts of acrylic acid, and 2 parts of 2-mercaptoethanol. was placed in a flask, the flask was purged with nitrogen, and then heated to 70°C. 0.1 part of 4.4°-azobisisobutyronitrile was added thereto, and polymerization was carried out until no heat generation was observed.

The obtained acrylic low molecular weight copolymer has a polymerization rate of 100.
%, viscosity (Brookfield viscosity, 30°C) 300
The average molecular weight (vapor pressure osmosis method) was 4400, and the number of hydroxyl groups per molecule calculated from the molecular weight was 2.0.

Reference example 2 80 parts of isooctyl acrylate and 20 parts of ethyl acrylate
A 20% ethyl acetate solution of an acrylic adhesive made by adding 1 part of a reaction product (dismodule) of trimethylolpropane and tolylene diisocyanate to 100 parts of a copolymer consisting of 12
A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having a thickness of 50 μm was obtained by drying at 0° C. for 3 minutes.

Example 1 100 parts of the acrylic low molecular weight copolymer obtained in Reference Example 1 and 100 parts of a prepolymer obtained by adding tolylene diisocyanate to polypropylene glycol with a molecular weight of 3000 were used, with an apparent density of 0.02 g/cm. An acrylic composition for forming a porous material of the present invention was obtained by uniformly mixing 3 parts of organic hollow particles having an average particle size of 50 mm and 0.1 part of dibutyltin dilaurate. Its viscosity was 350 boids.

The above-mentioned acrylic composition for forming a porous material was coated on a release paper to a thickness of one cylinder, and then heated at 50°C for 10 minutes, and then heated for 13 minutes.
A cured sheet was obtained by heat treatment at 0° C. for 10 minutes.

The formed cured sheet has an independent pore structure, has an apparent density of 0.62 g/c- and a thickness of 1 m, and has flexibility, cushioning properties, rebound resistance, impact mitigation properties, soundproofing properties of 11, It had excellent heat insulation, heat resistance, and weather resistance. Furthermore, one end of the cylinder (diameter 30M) was sealed with the cured sheet and water was poured into it to form a 500 mm water column, but no water leakage was observed and its waterproof properties were also compromised.

Comparative Example 1 Instead of the acrylic low molecular weight copolymer, molecular weight 11 O
A cured sheet was obtained according to Example 1 except that 00 polypropylene glycol was used.

Example 2 100 parts of the acrylic low molecular weight copolymer obtained in Reference Example 1, 8 parts of tolylene diisocyanate, 10 parts of α,α-azobisisobutyronitrile, and 0.5 parts of tin octylate. 0.1 part of silicone oil was uniformly mixed in a vacuum mixer to obtain an acrylic composition for forming porous materials of the present invention. Its viscosity was 340 boids.

The above acrylic composition for forming a porous material was placed on release paper for 1 m.
It was applied to a thickness of 11 mm, preheated at 100°C for 15 minutes, and then heated at 140°C for 30 minutes to form a foam.
It was cured to obtain a foamed cured sheet.

The formed cured sheet has an open foam structure and has an apparent density of 0.52 g/cn? The cushion had a thickness of 2 mm, and was excellent in flexibility, cushioning resistance, impact resistance, sound insulation, heat insulation, heat resistance, and weather resistance.

Example 3 The adhesive side of the adhesive sheet obtained in Reference Example 2 was pressed onto both sides of the cured sheet obtained according to Example 1 to obtain a pressure-sensitive adhesive tape of the present invention.

Example 4 On the acrylic adhesive layer of the adhesive sheet obtained in Reference Example 2, the acrylic composition for forming a porous material obtained in Example 1 was applied to a thickness of 1 m, and on the coated layer. A pressure-sensitive adhesive sheet similar to that described above was pasted through the pressure-sensitive adhesive layer, and this was
The pressure-sensitive adhesive tape of the present invention was obtained by heating at 130°C for 10 minutes and then at 130°C for 10 minutes. Note that the internal cured sheet was almost the same as in Example 1.

Example 5 On the acrylic adhesive layer of the adhesive sheet obtained in Reference Example 2, the acrylic composition for forming a porous material obtained in Example 2 was applied to a thickness of 1 + nn+, and this was heated at 100 ° C. 15
After preheating for a minute, the mixture was heat-treated at 140° C. for 30 minutes to foam and harden to obtain a pressure-sensitive adhesive tape of the present invention. The foam cured sheet inside was almost the same as in Example 2.

Example 6 The method of the present invention was carried out in the same manner as in Example 5, except that a pressure-sensitive adhesive sheet similar to that described above was attached to the coating layer of the acrylic composition for forming a porous material via the pressure-sensitive adhesive layer before preheating. A pressure adhesive tape was obtained.

Comparative Example 2 Reference Example 2 was applied to both sides of a foamed cured sheet obtained according to Example 2.
A pressure-sensitive adhesive tape was obtained by pressing the adhesive side of the adhesive sheet obtained in .

Comparative Example 3 A pressure-sensitive adhesive tape was obtained according to Comparative Example 2, except that an ether-type urethane foam (commercially available) having a thickness of 2 mm was used.

Evaluation test [Cured sheet 1 Dumbbell 3 from the cured sheet obtained in Example 1 or Comparative example 1
Test pieces were punched out using No. 1, and the initial pieces and those further heat-treated at 90° C. for 2 weeks were subjected to a tensile test at a tensile rate of 50 pus/min.

In addition, 10 cured sheets obtained in Example 1 or Comparative Example 1 were stacked, compressed by 30% using a jig, and in that state
After being kept in an atmosphere at 0° C. for one week, the jig was removed and left at room temperature for two days, and the height was measured to determine the recovery rate.

The results are shown in Table 1.

From Table 1, it can be seen that the cured sheets of Examples using the low molecular weight acrylic copolymers are excellent in flexibility, heat resistance, and cushioning properties.

■Pressure-sensitive adhesive tape] For the pressure-sensitive adhesive tapes having adhesive layers on both sides obtained in Example 3.4.6 and Comparative Example 2.3, the thickness of two aluminum plates was bonded via the pressure-sensitive adhesive tape. 0,5 mra
) with an adhesion area of 10IIIaxlOLII11, and then 500g, 1kg or 2k in an atmosphere of 80℃.
The time taken for one aluminum plate to fall by applying a load of 1.5 g was investigated.

The results are shown in Table 2.

Table 2 From Table 2, it can be seen that the pressure-sensitive adhesive tape of the example was a hard 1hi sheet (
It can be seen that the adhesive strength between the base material and the adhesive layer is excellent, and the creep resistance is excellent.

In addition, in the pressure-sensitive adhesive tapes of Comparative Examples 2 and 3, both broke (interlayer peeling) between the foam sheet (base material) and the adhesive layer.

Patent applicant: Nitto Electric Industry Co., Ltd.

Claims (1)

[Claims] 1. A functional group capable of reacting with an isocyanate is 1.6 to 3.
A porous material containing a low molecular weight acrylic copolymer having 5 pores, a polyfunctional isocyanate, and a pore-forming agent, which has a large number of pores and is capable of producing a flexible sheet-like cured product. Forming acrylic composition. 2. A pressure-sensitive adhesive tape comprising an acrylic pressure-sensitive adhesive layer adhered to a flexible sheet-like cured product having a large number of pores and comprising the acrylic composition for forming a porous material according to item 1. 3. The first layer is placed on the acrylic adhesive layer of the adhesive sheet.
3. The method for producing a pressure-sensitive adhesive tape according to item 2, which comprises applying the porous material-forming acrylic composition described in item 2 and heat-treating it. 4. The first layer is placed on the acrylic adhesive layer of the adhesive sheet.
A cured product, characterized in that the acrylic composition for forming a porous material described in 1. is coated, a pressure-sensitive adhesive sheet is further superimposed on the coated layer via an acrylic pressure-sensitive adhesive layer, and this is heat-treated. 3. The method for producing a pressure-sensitive adhesive tape according to item 2, which has an acrylic adhesive layer on both sides.